Abaixo está uma instrução que descreve uma tarefa de geração de SQL, combinada com uma entrada que fornece mais contexto sobre os esquemas de tabela disponíveis. Escreva o código SQL que responda adequadamente à solicitação
 ###Instrução: Qual é o total da grade associado a 18 voltas?
 ###Tabelas: CREATE TABLE 125cc_classification (125cc_classification_id AUTO_INCREMENT PRIMARY KEY, Rider VARCHAR, Manufacturer VARCHAR, Laps INT, Time/Retired VARCHAR, Grid INT) CREATE TABLE appearances_in_the_tour_de_france (appearances_in_the_tour_de_france_id AUTO_INCREMENT PRIMARY KEY, Year INT, Stage INT, Category INT, Start VARCHAR, Finish VARCHAR, Leader at the summit VARCHAR) CREATE TABLE january_secondary_phase (january_secondary_phase_id AUTO_INCREMENT PRIMARY KEY, Round INT, Name VARCHAR, Position VARCHAR, School VARCHAR, Signed VARCHAR) CREATE TABLE pdc_premier_event_finals:_5_1_title_4_runner-ups (pdc_premier_event_finals:_5_1_title_4_runner-ups_id AUTO_INCREMENT PRIMARY KEY, Outcome VARCHAR, Year INT, Championship VARCHAR, Opponent in the final VARCHAR, Score (l) = score in legs, (s) = score in sets. VARCHAR) CREATE TABLE 2010_ama_supercross_motocross_season (2010_ama_supercross_motocross_season_id AUTO_INCREMENT PRIMARY KEY, Round INT, Date VARCHAR, Place VARCHAR, Finished VARCHAR, Total Points INT, Standing VARCHAR)  
SELECT COUNT Grid FROM 125cc_classification WHERE Laps = 18